Method and apparatus for protecting the legitimacy of an article

ABSTRACT

A method, an apparatus and a computer program product are disclosed for protecting the legitimacy of an article ( 100 ), and in particular an electronic document, against forgery or fraud. Such articles include passports, credit cards, bank notes, lottery tickets, secure forms. The method includes the following steps: several watermarks ( 204, 224, 244 ) are generated independently ( 304, 306, 308 ) by different cryptographic watermarking mechanisms controlled utilising information permanently associated within the article or product ( 100 ); and each watermark is embedded in a linked cryptographic manner ( 160, 162, 164 ). Subsequently, the watermarks can be scanned and digitised ( 410 ). The authenticity of the article ( 100 ) can be determined by verifying the correctness of extracted watermarks and the encryption links ( 160, 162, 164 ) among them. Also disclosed is a method of embedding an invisible watermark ( 714 ) in an official seal ( 712 ) incorporated in an electronic article or document ( 700 ).

FIELD OF THE INVENTION

The present invention relates to systems for protecting the legitimacyof an article and in particular to systems for verifying theauthenticity of an electronic document or article against forgery.

BACKGROUND

Verifying the authenticity of a document or article is a well-knownproblem that is made increasingly more difficult with the widespread useof sophisticated reproduction technologies. This is particularly thecase in relation to digital media. Sophisticated reproduction systemsare readily available. Even home computer systems are capable ofperforming reproduction functions that until not very long ago were onlycapable of being performed by large institutions, such as governmentagencies and large corporations, due to the resources that wererequired. Thus, technology capable of facilitating the counterfeiting ormisuse of documents is widespread. Consequently, attempts have been madeto provide methods and systems for verifying the authenticity ofdocuments and articles such as identification cards against forgery orfraud.

U.S. Pat. No. 5,719,939 describes a system and method for verifying thelegitimacy of a product against forgery. A pattern of overlyingindividual fibres is embedded in a transparent base material, so thatthe fibres form differing geometrical configurations. The fibres arecapable of being optically scanned through a surface of the transparentbase material. Subsequently, an inspector may scan the product andcompare the obtained data with the stored data in an attempt to verifythe authenticity of the product.

However, the security of the method disclosed in U.S. Pat. No. 5,719,939is heavily dependent on the different geometrical configurations of theparticular fibres. If the configurations are too simple, security cannotbe guaranteed. On the other hand, if the configurations are too complex,the costs of the system increase significantly.

U.S. Pat. No. 5,742,685 discloses a method for verifying anidentification card and recording a verification of the same. An imageof a person whom the identification card is to identify is scanned toproduce a digital signal associated with a text message. They arecompressed, encrypted, and then coded as a two-dimensional barcode. Thebarcode is then printed on the back of the identification card. Toverify the validity of the card, the barcode is scanned, decoded,decrypted, expanded and displayed. To perform verification, theresulting displayed image and text are compared with the correspondinginformation printed on the card.

While the method of U.S. Pat. No. 5,742,685 utilises a cryptographicconnection between the printed image and the text on the one hand andthe printed barcode on the other, there are several disadvantages ofthis method, relating to the practicability and complexity of themethod. One such difficulty is how to compress an entire image to a sizethat satisfies the requirements of encryption and barcode encoding,while maintaining image quality. Significant compression can cause asignificant degradation in the capacity to the recovered image with theoriginal image. A further disadvantage is that a separateencryption/decryption key is required

There is therefore a need for an improved technique of verifying theauthenticity of an article, especially an electronic document.

SUMMARY

In accordance with a first aspect of the invention, a method ofembedding linked watermarks in an article requiring protection againstforgery is disclosed. The method includes the steps of: extractinginformation from a first portion of the article; encrypting theextracted information from the first portion; generating a watermarkusing the encrypted information; rendering the watermark to a secondportion of the article; and repeating the extracting, encrypting,generating and rendering steps with another portion of the article untilall relevant information of the article has been processed and acryptographic link is formed thereby.

Preferably, the watermark is generated based on a selected watermarkgenerating mechanism dependent upon the encrypted information. Further,each of the watermarks can be generated based on different watermarkgeneration mechanism. Still more preferably, seeds for generating awatermark can be obtained from only one portion of the article orseveral selected portions of the article.

Preferably, the information is extracted directly from text and/or fromone or more invariant features of an image. The image can depictbiometric data of a person associated with the article.

Preferably, the article is an electronic document. It can also be aprinted document.

In accordance with a second aspect of the invention, there is disclosedan apparatus for embedding linked watermarks in an article requiringprotection against forgery. The apparatus includes: a device forextracting information from a first portion of the article; a device forencrypting the extracted information from the first portion; a devicefor generating a watermark using the encrypted information; a device forrendering the watermark to a second portion of the article; and a devicefor controlling repeated operation of the extracting, encrypting,generating and rendering devices with another portion of the articleuntil all relevant information of the article has been processed and acryptographic link is formed thereby.

In accordance with a third aspect of the invention, there is disclosed acomputer program product having a computer readable medium having acomputer program recorded therein for embedding linked watermarks in anarticle requiring protection against forgery, the computer programproduct including: a module for extracting information from a firstportion of the article; a module for encrypting the extractedinformation from the first portion; a module for generating a watermarkusing the encrypted information; a module for rendering the watermark toa second portion of the article; and a module for controlling repeatedoperation of the extracting, encrypting, generating and renderingmodules with another portion of the article until all relevantinformation of the article has been processed and a cryptographic linkis formed thereby.

In accordance with a fourth aspect of the invention, there is disclosedan article requiring protection against forgery or fraud. The articleincludes: two or more portions for containing information, theinformation including text, biometric data, or both; two or morewatermarks, each watermark printed in a respective one of the portionsand being dependent upon information in a different portion, whereby acryptographic link is formed between the two or more portions.

Preferably, the article is an electronic document. It can also be aprinted document.

In accordance with a fifth aspect of the invention, there is disclosedan article requiring protection against forgery or fraud. The article isformed by the steps of: extracting information from a first portion ofthe article, the article having two or more portions for containinginformation, the information including text, biometric data, or both;encrypting the extracted information from the first portion; generatinga watermark using the encrypted information; rendering the watermark toa second portion of the article; and repeating the extracting,encrypting, generating and rendering steps with another portion of thearticle until all relevant information of the article has been processedso that two or more watermarks are formed, each watermark being renderedin a respective one of the portions and being dependent upon informationextracted from a different portion, whereby a cryptographic link isformed between the two or more portions.

In accordance with a sixth aspect of the invention, there is disclosed amethod of forming an article requiring protection against forgery. Themethod includes the steps of: generating an invisible watermarkdependent upon information contained in the article; and rendering thewatermark within an official seal placed on the article, the officialseal being a securely controlled item of an authority.

Preferably, the article is an electronic document. It can also be aprinted document.

Preferably, the method includes the steps of: extracting informationfrom a portion of the article; and encrypting the extracted information.The information can be extracted directly from text, or from one or moreinvariant features of an image. The image can depict biometric data of aperson associated with the article.

In accordance with a seventh aspect of the invention, there is disclosedan apparatus for forming an article requiring protection againstforgery. The apparatus includes: a device for generating an invisiblewatermark dependent upon information contained in the article; and adevice for rendering the watermark within an official seal placed on thearticle, the official seal being a securely controlled item of anauthority.

In accordance with an eighth aspect of the invention, there is discloseda computer program product having a computer readable medium having acomputer program recorded therein for forming an article requiringprotection against forgery. The computer program product includes: amodule for generating an invisible watermark dependent upon informationcontained in the article; and a module for rendering the watermarkwithin an official seal placed on the article, the official seal being asecurely controlled item of an authority.

In accordance with a ninth aspect of the invention, there is disclosedan article requiring protection against forgery or fraud. The articleincludes: a portion containing information, the information includingtext, biometric data, or both; an official seal placed on the article,the official seal being a securely controlled item of an authority; andan invisible watermark dependent upon the information and being renderedwithin the official seal.

Preferably, the article is an electronic document. It can also be aprinted document.

In accordance with a tenth aspect of the invention, there is disclosedan article requiring protection against forgery or fraud. The article isformed by the steps of: generating an invisible watermark dependent uponinformation contained in the article, the information including text,biometric data, or both; and rendering the watermark within an officialseal placed on the article, the official seal being a securelycontrolled item of an authority.

In accordance with an eleventh aspect of the invention, there isdisclosed a method of verifying the legitimacy of an article againstforgery. The method includes the steps of: inputting the article as twoor more portions; extracting at least one watermark from each portion;determining a watermark from information in each portion; comparing theextracted watermark from one portion with the determined watermark froma different portion to determine if a corresponding cryptographic linkis found; and repeating the comparing step until all portions of thearticle have been processed, the article being verified as a legitimatearticle if all cryptographic links are found between the two or moreportions.

Preferably, the method includes the steps of: scanning the product; anddividing the scanned product into two or more portions. It can alsoinclude the step of scanning information from a portion of the productto reconstruct a seed to a generated watermark using a cryptographictechnique carried out in a process of embedding a watermark in theportion. More preferably, the method includes the step of: extracting aninvariant feature from the scanned information to reconstruct the seed.The extracted, invariant feature can include biometric data.

Preferably, the method also includes the step of decrypting the scannedinformation to reconstruct the seed. Optionally, a cryptographic linkcan be a self-circle, that is referring back to itself.

In accordance with a twelfth aspect of the invention, there is disclosedan apparatus for verifying the legitimacy of an article against forgery.The apparatus includes: a device for inputting the article as two ormore portions; a device for extracting at least one watermark from eachportion; a device for determining a watermark from information in eachportion; a device for comparing the extracted watermark from one portionwith the determined watermark from a different portion to determine if acorresponding cryptographic link is found; and a device for repeatingthe comparing step until all portions of the article have beenprocessed, the article being verified as a legitimate article if allcryptographic links are found between the two or more portions.

In accordance with a thirteenth aspect of the invention, there isdisclosed a computer program product having a computer readable mediumhaving a computer program recorded therein for verifying the legitimacyof an article against forgery. The computer program product includes: amodule for inputting the article as two or more portions; a module forextracting at least one watermark from each portion; a module fordetermining a watermark from information in each portion; a module forcomparing the extracted watermark from one portion with the determinedwatermark from a different portion to determine if a correspondingcryptographic link is found; and a module for repeating the comparingstep until all portions of the article have been processed, the articlebeing verified as a legitimate article if all cryptographic links arefound between the two or more portions.

In accordance with a fourteenth aspect of the invention, there isdisclosed a method of verifying the legitimacy of an article againstforgery. The method includes the steps of: extracting at least oneinvisible watermark from an official seal, the official seal being asecurely controlled item of an authority; and comparing the extractedwatermark with verification information to determined if the extractedwatermark matches the verification information indicating that thearticle is legitimate.

Preferably, the verification information is information identifying theauthority.

Preferably, the method includes the step of generating a watermarkdependent upon information forming part of the article to provide theverification information. The information forming part of the articlecan be biometrics data.

Preferably, the method includes the step of decrypting the watermark.

In accordance with a fifteenth aspect of the invention, there isdisclosed an apparatus for verifying the legitimacy of an articleagainst forgery. The apparatus includes: a device for extracting atleast one invisible watermark from an official seal, the official sealbeing a securely controlled item of an authority; and a device forcomparing the extracted watermark with verification information todetermined if the extracted watermark matches the verificationinformation indicating that the article is legitimate.

In accordance with a sixteenth aspect of the invention, there isdisclosed a computer program product having a computer readable mediumhaving a computer program recorded therein for verifying the legitimacyof an article against forgery. The computer program product includes: amodule for extracting at least one invisible watermark from an officialseal, the official seal being a securely controlled item of anauthority; and a module for comparing the extracted watermark withverification information to determined if the extracted watermarkmatches the verification information indicating that the article islegitimate.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described hereinafter with reference tothe drawings, in which:

FIG. 1 is a block diagram illustrating an article according to the firstembodiment of the invention;

FIG. 2 is a symbolic diagram depicting the formation of a cryptographicwatermark link in accordance with the first embodiment;

FIG. 3 is a flow diagram illustrating a method of forming and embeddingwatermarks in accordance with the first embodiment;

FIG. 4 is a flow diagram illustrating a method of authentication inaccordance with the first embodiment;

FIG. 5 is a flow diagram illustrating a typical method of extractinginvariant biometric features, which may be practised in the methods ofFIGS. 3 and 4;

FIG. 6 is a flow diagram illustrating a typical method of generating awatermark, which may be practised in the methods of FIGS. 3 and 4; and

FIG. 7 is a block diagram illustrating an article according to thesecond embodiment of the embodiment.

DETAILED DESCRIPTION

A method, apparatus, and computer program product for verifying theauthenticity of an electronic document or article are disclosed.Further, an improved electronic document is disclosed. In the followingdescription of several embodiments, numerous specific details such asparticular watermarking techniques are described in order to provide amore thorough description of those embodiments. It will be apparent,however, to one skilled in the art that the present invention may bepractised without those specific details. In other instances, well-knownfeatures such as particular biometrics data, for example, have not beendescribed in detail so as not to obscure the invention.

In broad terms, the embodiments of the invention provide a system forverifying the legitimacy of an electronic product against forgery orfraud. The embodiments of the invention can be used to verify theauthenticity of articles formed from electronic data, includingidentification cards and other security related items. Other types ofproducts that can be protected include passports, credit cards, personalidentification cards, banknotes, checks or negotiable instruments,certificates, security forms, lottery tickets, and the like. Generally,the embodiments of the invention can be used in any electronic orphysical documents relating to security.

In one embodiment, a watermark dependent upon the source electronicproduct is embedded in an electronic seal or stamp, which isincorporated in or embedded on the electronic product. This electronic“seal” or “stamp” is a controlled marking establishing the authority ofthe person verifying the electronic product's authenticity. For example,a notary public could embed their official electronic seal on anelectronic document. The official seal is itself preferably visible. Toensure that tampering of the electronic document can be detected afterthe document is certified or endorsed with the stamp, an invisiblewatermark containing information about the authority. Alternatively, theinvisible watermark can be dependent upon a portion of, portions of, orthe entire document is embedded in the stamp. Thus, the authenticity ofthe document can be verified. In the latter case, subsequent changes tothe document can be detected since the watermark in the seal will notmatch a watermark that is generated dependent upon the modified data.

In another embodiment, relevant information in portions of an electronicproduct are linked to other respective portions of the document in acryptographic way based on invisible or visible watermarks. That is,information in a first portion of an electronic document, for example,is embedded as an invisible watermark in a second portion of thedocument. Information in the second portion is embedded as a watermarkin a third portion. Likewise, information in the third portion can beembedded as a watermark in the first portion. Numerous othercombinations and arrangements are possible.

Preferably, the product has a unique feature representation of abiometric characteristic of its owner (e.g. a facial image) printed on afirst portion of the product. Using a facial recognition method,invariant features can be extracted from the first representation toform the second representation of biometric characteristics of theowner. The second representation is coded and encrypted as input for thefirst watermark generator. The first watermark generated (the thirdrepresentation of a biometric characteristic of the owner) is printedonto a second portion of the product.

The second portion of the product may have also a first unique featurerepresentation of another biometric characteristic of the owner, such asa picture of the person's fingerprint printed on the second portion.Using a fingerprint recognition method, invariant features can beextracted from-the above first representation (i.e. fingerprint picture)to form the second representation of the biometric characteristic of theowner. The second representation is then coded and encrypted as input ofa second watermark generator. The second watermark generated (the thirdrepresentation of a biometric characteristic of the owner) is printedonto a third portion of the product. This process can be repeated anynumber of times in a similar fashion for other portions of the product.This process continues until a coded and encrypted representation fromthe last portion is printed on the first portion of the product.

A cryptographic link is thereby formed. The security of the product'sauthentication is increased not only by verifying it through traditionalauthentication means, but also by verifying the correctness of theformed cryptographic link. Preferably, the cryptographic link can beimplemented in a self-circle way. That is, unique information isextracted from a portion, and a corresponding watermark is formed andembedded into the same portion to protect the portion from alteration.

Again, the first representation of biometric characteristic can be animage of the persons face or fingerprint. The second representation canbe invariant extracted features of the first representation. The thirdrepresentation is a watermark generated from the second representation.

Optionally, other information related to the product owner's identity,including the person's ID number, birth date, birthplace, and the like,is appended to the source of the representation at a differentrepresentation level. Still further information can be used related towhole operation, such as the embedding time and the embedding place, canbe appended to the source of the representation in different portions ofthe product. Optionally, the verification can be done at differentlevels based on different requirements of particular applications.

First Embodiment

FIG. 1 is a block diagram depicting an article 100 containing securityinformation in accordance with a first embodiment of the invention. Thedepicted exemplary article 100 is a passport. However, the article canbe any of numerous products requiring protection against forgery,including a credit card, a bank note, a lottery ticket, a legaldocument, a driver's license, a birth certificate, etc. Forming linkedcryptographic watermarks in several portions of the article increasesthe verifiable authenticity of the article 100 requiring protectionagainst forgery or any other unauthorised modification.

The depicted passport 100 of FIG. 1 includes three regions, areas orportions 102, 120 and 140. For example, the portion 102 of the passport100 is the cover of a passport, which normally is a separate sheet. Theother portions 120 and 140 of the article or product 100 can be separateor overlapping parts of the same sheet, which is different from that ofportion 102. Numerous other possibilities can be envisaged and will bereadily apparent to those skilled in the art in view of the disclosureprovided herein. In FIG. 1, the portions 120 and 140 do not overlap.

The first portion 102 of the passport 100 is marked with information 104that can be used to watermark one or more other portions 120 and 140 ofthe article 100. The information 104 includes a first identificationportion 106 and the name of the country or state 108 for which thepassport is issued.

The second portion 120 of the passport 100 contains a person'sphotographor other depiction of their likeness 122, various pieces ofdata 124 about the passport and the person, and another identificationportion 126. The various pieces of data 124 are typically associatedwith the person and include in this example the passport number, thename of the person, and both the place and date of issue of thepassport.

The third portion of the passport 100 contains biometric data 142 suchas the person's fingerprint, personal particulars 144 and a thirdidentification portion 146. The personal particulars in this exampleinclude the person's age, blood group, and height.

In the article 100, one or more messages or pieces of information thatare likely to be included in the article 100 (e.g. the passport) can beutilised to generate the linked watermarks or cryptographic link.Watermarking links formed in this manner significantly increase thesecurity of the article or product 100 against undetected forgery. Atthe same time, the conventional means employed in the article 100against forgery can be retained.

In the first portion 102 of the passport 100, the message to beextracted can be the “Name of Country” 108. The extracted message isencrypted. The encrypted message is then used to generate a firstwatermark based on the first selected watermark generating mechanism. Inturn, the first watermark is printed or otherwise reproduced in at leastthe second portion 120. An arrow 160 extending from the first portion102 to the second portions 120 of the passport 100 generally depictsthis method in accordance with the first embodiment.

In the second portion 120 of the passport 100, the photograph ordepiction 122 of the person can be used as information to generate awatermark for the third or first portions 140, 102. For example, abiometrics recognition engine can be used with the person's facecontained in the image 122 to extract one or more invariant features ofthe person. One of the invariant features alone, or several invariantfeatures combined, can be encrypted (for example, by hashing). Theencrypted message is used to generate the second watermark based on asecond selected watermark generating mechanism. The second generatedwatermark is rendered or printed onto the third portion 140 of thepassport 100, where the person's fingerprint picture and associatedmessages are located. Another arrow 162 extending from the secondportion 120 to the third portion 140 of the passport 100 generallydepicts this process.

In turn, yet another biometric recognition engine can be used with thefingerprint 142 to extract its invariant features. Again, one of theseinvariant features alone or several invariant features combined can beencrypted (for example, by hashing) with the above messages. Theencrypted message is used to generate a third watermark based on thethird selected watermark generating mechanism. The third generatedwatermark is printed onto the first portion 102 of the article 100. Inthis manner, a cryptographic watermarking link is formed between thevarious portions 102, 120, 140 of the passport 100.

FIG. 2 provides a symbolic depiction of the method in accordance withthe first embodiment. Various portions of an article requiringprotection against forgery or unauthorised modification are depicted bydashed-line ovals 200, 220, 240 and 260, each of which is labelled area1, area 2, area 3, . . . , area n. The number n may be dependent on theparticular application of the method and can be selected by the user.Each area 200, 220, 240 is depicted containing a circle 202, 222, 242representing extraction of a feature for the area and encryption of theextracted feature. The area 200, 220, 240 also contains another circle204, 224, 244 depicting printing or rendering of a watermark fromanother area. The area 260 is meant to be a general depiction of anotherarea and therefore its details are not shown. The dashed arrowsextending between the areas 200, 220, 240, 260 indicate the relationshipbetween features extracted and encrypted 202, 222, 242 from one areabeing used to print or render a watermark 204, 224, 244 of at least oneother different area 200, 220, 240, 260.

With reference to the specific example of FIG. 1 and the more abstractdepiction of FIG. 2, a process of authenticating an article embeddedwith linked watermarks according the first embodiment is explained.During the authentication process, portions of the article 100, forexample, are scanned and digitised. Firstly, each portion 102, 120, 140is checked to detect whether or not an embedded watermark is located inthe relevant portion. If an embedded watermark is not detected in one ormore of the portions 102, 120, 140, this result indicates that thearticle is a forgery. Furthermore, an extracted copy of the watermarkdetected in a portion under scrutiny is checked against a correspondingwatermark, which is derived on the fly using a combined and encryptedmessage obtained from another relevant portion of the article. If thewatermark rendered in the portion does not match the on-the-flywatermark, this indicates that the article is also a forgery. Theforegoing authentication or verification process is carried out untilall portions of the article 100 are checked. This method of verifyingthe legitimacy of an article against forgery or fraud does not affectany conventional or existing security features or means used in thearticle to protect against forgery.

FIG. 3 is a flow diagram illustrating the method of forming andembedding linked watermarks in an article in accordance with the firstembodiment of the invention. Processing commences in step 300. In step302, a “working area” or portion of the article is selected forprocessing. For example, the first portion 102 of the passport 100 inFIG. 1 can be selected. In step 304, an encrypted message extracted fromthe portion is generated. In particular, sub-step 304A extracts afeature from the portion. Preferably, this involves extracting abiometrics feature. In sub-step 304B, one ore more extracted featuresare selected for encryption and encrypted. One skilled in the art willappreciate that the sub-steps 304A and 304B can be implemented asseparate steps. In step 306, a watermark is formed or generated usingthe encrypted message. While step 306 as depicted in FIG. 3 onlyindicates that a watermark is formed, it will be appreciated from thedisclosure herein that one or more watermark generation techniques canbe employed. Preferably, different watermark generation techniques areutilised to generate each watermark in different “working areas”. Onemethod of forming a watermark is to produce a noise-like random patternusing the extracted message and combine the original content and thegenerated pattern under the condition that no change in the originaldocument can be readily perceived by the HVS. An example of such atechnique is disclosed by Cox, I J, Killan, J, Leighton, T and Shamoon,T, Secure Spread Spectrum Watermarking for Multimedia, Tech. Rep. 95-10,NEC Research Institute.

In step 308, the generated watermark is rendered or embedded into atleast one other “working area”. For example, the watermark derived fromthe portion 102 can be rendered or embedded in the second portion 120 ofthe article 100. In decision block 310, a check is made to determine ifall portions of the article have been processed (i.e. is processingcomplete?). If decision block 310, returns false (NO), processingcontinues at step 302 and another portion of the article is selected asthe “working area” for processing. Otherwise, if decision block 310returns true (YES), processing terminates in step 312. Thus, theembedding method of the first embodiment is carried out until allworking areas have been processed. The method produces a more securearticle that can be better protected against undetected forgery or otherunauthorised modification.

FIG. 4 is a flow diagram of authenticating or verifying an articleembedded with linked watermarks according the first embodiment.Processing commences in step 400. In step 402, a “working area” orportion of the article is selected for processing. Preferably, steps 404and 406 on the one hand and steps 410 and 412 on the other are performedsubstantially in parallel as indicated graphically in FIG. 4 where thetwo groups of steps form parallel branches of operations following step402. However, one skilled in the art will appreciate that this need notbe the case, and the groups of steps can be carried out sequentiallyinstead.

In step 410, a watermark is extracted from the “working area” selectedin step 402. In decision block 412, a check is made to verify thewatermark obtained in step 410. If decision block 412 returns false(NO), processing preferably continues at step 420, in which a warningmessage is issued, before processing terminates in step 424. Step 420 isindicated with dashed lines to show that the step is optional anddifferent processing may be implemented or omitted altogether withoutdeparting from the scope and spirit of the invention. Otherwise, ifdecision block 412 returns true (YES), processing continues at step 414.

In step 404, one or more features are extracted from another workingarea, different from the one selected in step 402. The working area forstep 404 is the portion of the article from which the watermarkextracted from the selected working area in step 410 is derived.Preferably, a biometric feature(s) is extracted. In step 406, oneextracted feature or a combination of features extracted from theworking area of step 404 are selected and encrypted. Processing thencontinues at step 414.

In step 414, a correlation is carried out between the verified watermarkextracted from the selected working area and the output of step 406. Indecision block 416, a check is made to determine whether or not thecorrelation result exceeds a predefined threshold. If decision block 416returns false (NO), this indicates that the article is a forgery.Processing then preferably continues at step 420, and a warning messageis given before processing terminates in step 424. Otherwise, ifdecision block 416 returns true (YES), processing continues at decisionblock 418. In decision block 418, a check is made to determine if allworking areas of the article 100 have been processed. If decision block418 returns false (NO), processing continues at step 402 and anotherremaining working area is selected for processing. Otherwise, if thedecision block 418 returns true (YES), processing preferably continuesat optional step 422. In this manner, the authentication process iscarried out until a selected working area fails or all working areas areprocessed. In step 422, a message that the article is authenticated orhas “passed” is output. Step 422 is also indicated with dashed lines toshow that the step is optional, and different processing may beimplemented or omitted altogether without departing from the scope andspirit of the invention. Processing then terminates in step 424.

FIG. 5 is a flow diagram illustrating an exemplary process of extractinginvariant biometrics feature, which can be practised with theembodiments of the invention. Processing commences with the input ofbiometrics data, such as a person's facial image 500 or fingerprint, forexample. Other types of biometrics data may be practised with theembodiments of the invention without departing from the scope and spiritof the invention. In step 504, the biometrics data (e.g. facial image500 or fingerprint 502) is electronically scanned and digitised.Optionally, step 506 may be carried out if necessary to pre-process thedigital data. This can involve filtering, or enhancing the data content,for example. Other conventional techniques of processing digital datacan be practised without departing from the scope and spirit of theinvention.

In step 508, the digital data (i.e. image) is normalised in both spaceand intensity based on predefined rules and landmarks. In step 510, oneor more features are extracted from the normalised data. In step 512,recognition processing of the extracted features is carried out toidentify invariant features. Any of a number of recognition methods canbe practised. For some recognition methods, the recognition base 514 maybe required as input to the recognition engine in step 512. For example,in a facial recognition system, an eigenface technique can be practised.The eigenfaces (recognition base) are previously produced by trainingfacial samples. The invariant features can be determined by computing aprojection of an input facial image onto the eigenfaces. As this isoptional dependent upon the recognition method used, it is depictedusing dashed lines. Finally, in step 512, the invariant biometricsfeatures 516 are obtained using the recognition engine. The invariantfeatures 516 can be output to the watermark generator. Normally, thesefeatures 516 have a size of a few hundred bytes.

FIG. 6 is a flow diagram illustrating a method of generating awatermark, which can be practised with the embodiments of the invention.Biometrics data or information 600 and other appending information 602alone or together can be provided as input to the procedure. Suchinformation is derived from a portion or working area of an article 100.In step 604, after the invariant biometric information and/or otherappending information are obtained, the information is encrypted. Any ofa number of encryption techniques can be practised without departingfrom the scope and spirit of the invention. The particular encryptiontechnique is represented as the algorithm selection 606 that is providedas input to step 604. The encryption technique may be fixed or selectedon the fly dependent on the data to be encrypted. Exemplary encryptiontechniques include secret mapping, hashing, and cryptographic methodssuch as those disclosed by Schneier, Bruce, Applied Crotography:Protocols, Algorithms, and Source Code in C, John Wiley & Sons, Inc.,1996. The selection of different algorithms can be controlled dependentupon particular applications and security requirement to increaseoverall security.

In step 608, a random pattern is generated based on a selected watermarkgenerating mechanism 610. The selection can be done so that the randompattern is controlled or dependent upon the extracted message. Differentrandom number generators can be chosen to increase overall security.

In step 612, a final watermark is formed dependent upon perceptualanalysis 614 on the area to be embedded based on the Human Vision System(HVS). The strength of the watermark is also controlled by therequirements of the particular application or system requirements 616.Thus, step 612 adjusts the watermark generated in step 608 dependentupon the area embedded analysis 614 and system requirements 616. Forexample, by checking Discrete-Cosine Transform (DCT) or Fast FourierTransform (FFT) components within a preselected block size, the contentof the affected area can be roughly classified. A stronger or morenoticeable watermark can be embedded in an area of high texture, and aweaker or less noticeable watermark can be embedded in a low texture orperhaps blank area.

In step 618, the adjusted watermark is printed, output or otherwiseembedded in the assigned portion or working area. In this connection,FIGS. 1 and 2 illustrate the relationships between the generation ofwatermarks using data from one area and the embedding of the watermarkin another area. The encryption used in the first embodiment is used notonly for the purpose of concealment but also for the purpose ofverification of the article or product 100. As biometric features andrecognition/extraction techniques are known, those skilled in the artwill appreciate that the selection and encryption of the extractedbiometrics information 600 and other appended messages 602 are helpfulto guarantee the security of watermark generators and the whole system.Meanwhile, the authentication is carried out using the encryptedselected message and extracted watermark. This is like verifying adigital signature.

The watermarking process and the corresponding watermark extractionprocess according to the first embodiment of the invention can beimplemented in hardware or software form. The functionality of theprocesses can be implemented as electronic or software modules, thelatter capable of being carried out using a computer. For example, theembodiment can be implemented as a computer program product. A computerprogram for protecting the legitimacy of an article can be stored on acomputer readable medium. Likewise, the computer program can be one forverifying the legitimacy of an article. In each case, the computerprogram can be read from the medium by a computer, which in turn carriesout the operations of the computer program. In yet another embodiment,the method depicted in FIG. 3 can be implemented as-an ApplicationSpecific Integrated Circuit (ASIC), for example. The methods are capableof being implemented in a number of other ways, which will be apparentto those skilled in the art in view of this disclosure, withoutdeparting from the scope and spirit of the invention.

Also, commercial printers and scanners can be used to practice theembodiments of the invention and satisfy the requirements of the system.For example, an HP Laser Jet 5 Printer offers true 600-dpi printing withresolution enhancement technology (RET), MicroFine toner, and 120 levelsof grey of the smooth. A report on image quality tests of Primascan 5100Greyscale Scanner, for example, points out that this scanner can achievea greyscale range about 200 levels and a resolution about 500 dpi.Equipment of this type is readily available to the public. The foregoingis merely exemplary of the range-of products that can be used topractice the embodiments of the invention.

Second Embodiment

FIG. 7 is a block diagram depicting an article 700 containing securityinformation according to the second embodiment. The depicted exemplaryarticle 700 is a passport. However, the article can be any of numerousproducts requiring protection against forgery, including a credit card,a bank note, a lottery ticket, a legal document, a driver's license, abirth certificate, etc. Embedding an invisible watermark in an officialseal increases the verifiable authenticity of the article 700 requiringprotection against forgery or any other unauthorised modification.

The passport 700 is depicted as a single sheet, or portion, 702. Itincludes an identification portion 704 and the name of country 708 in afirst area 704 indicated by a dashed line. It also contains a facialimage 710 of the passport holder. The “Name of Country” 708 can beextracted to form a watermark. Likewise, this can be done using theidentification portion alone or with the name of the country. Also, theperson's picture 710 can be used to form a watermark alone or with theother information. If the facial image 710 is used, invariant featuresof the facial image 710 are extracted using any of a number oftechniques well known to those skilled in the art. The resultingextracted message (i.e., the name of the country 708, identificationportion 706 and/or invariant extracted features of image 710) isencrypted. That is a digested or encrypted message is formed. This canbe done using a hash function or other cryptographic technique. Theencrypted message is then used to generate an invisible watermark.

To verify the passport as being properly issued, an official seal 712 isplaced on the passport sheet 702. The exemplary seal 712 includes amarking indicating its official nature, the date it is embossed orembedded on the sheet, and the signature of the signing authorisedperson. Numerous other possibilities for seals exist, including those ofa notary public, justice of the peace, a tax official, and the like.Preferably, the seal is an electronic one. A dashed-line portion 714indicates that the watermark formed from the extracted message isembedded in the seal and is invisible. By embedding a watermark 714within an official seal 712, it can be ensured that the document hasbeen properly averred to or authorised and that its contents have notbeen changed and only contain the information that the authorisingauthority considered. In this manner, a certifiable official seal isprovided.

Alternatively, a watermark can be embedded in the seal containinginformation about the authority alone or in combination with informationdescribed above. The invisible watermark authenticates and protects theowner of the seal that is applied. Only the authority has access to anunwatermarked copy of the seal. All other copies of the seal availableto the public are embedded with an invisible watermark.

As described hereinbefore with reference to the first embodiment, thewatermarking process and the corresponding watermark extraction processaccording to the second embodiment of the invention can be implementedin hardware or software form.

The foregoing embodiments of the invention provide an electronic seal ofsorts, by which an electronic or printed document can be certified asauthentic. In particular, articles providing protection against fraudforgery, and a method, an apparatus and a computer program product forprotecting the legitimacy of an article have been described. Acorresponding method, apparatus and computer program product have alsobeen disclosed for verifying the legitimacy of an article. While onlyseveral embodiments have been set forth, it shall be apparent to thoseskilled in the art, in view of the disclosure herein, that numerouschanges and/or modifications can be made without departing from thescope and spirit of the invention.

The claims defining the invention are as follows:
 1. A method ofembedding linked watermarks in an article requiring protection againstforgery, said method including the steps of: extracting information froma first portion of said article; encrypting said extracted informationfrom said first portion; generating a watermark using said encryptedinformation; rendering said watermark to a second portion of saidarticle; and repeating the extracting, encrypting, generating andrendering steps with another portion of said article until all relevantinformation of said article has been processed and a cryptographic linkis formed thereby.
 2. The method according to claim 1, wherein saidwatermark is generated based on a selected watermark generatingmechanism dependent upon said encrypted information.
 3. The methodaccording to claim 2, wherein each of said watermarks is generated basedon different watermark generation mechanism.
 4. The method according toclaim 3, wherein seeds for generating a watermark are from only oneportion of said article or several selected portions of said article. 5.The method according to claim 1, wherein said information is extracteddirectly from text.
 6. The method according to claim 1, wherein saidinformation is extracted from one or more invariant features of animage.
 7. The method according to claim 6, wherein said image depictsbiometric data of a person associated with the article.
 8. The methodaccording to claim 1, wherein said article is an electronic document. 9.An apparatus for embedding linked watermarks in an article requiringprotection against forgery, said apparatus including: means forextracting information from a first portion of said article; means forencrypting said extracted information from said first portion; means forgenerating a watermark using said encrypted information; means forrendering said watermark to a second portion of said article; and meansfor repeating the extracting, encrypting, generating and rendering stepswith another portion of said article until all relevant information ofsaid article has been processed and a cryptographic link is formedthereby.
 10. The apparatus according to claim 9, wherein said watermarkis generated based on a selected watermark generating mechanismdependent upon said encrypted information.
 11. The apparatus accordingto claim 10, wherein each of said watermarks is generated based ondifferent watermark generation mechanism.
 12. The apparatus according toclaim 11, wherein seeds for generating a watermark are from only oneportion of said article or several selected portions of said article.13. The apparatus according to claim 9, wherein said information isextracted directly from text.
 14. The apparatus according to claim 9,wherein said information is extracted from one or more invariantfeatures of an image.
 15. The apparatus according to claim 14, whereinsaid image depicts biometric data of a person associated with thearticle.
 16. The apparatus according to claim 9, wherein said article isan electronic document.
 17. A computer program product having a computerreadable medium having a computer program recorded therein for embeddinglinked watermarks in an article requiring protection against forgery,said computer program product including: means for extractinginformation from a first portion of said article; means for encryptingsaid extracted information from said first portion; means for generatinga watermark using said encrypted information; means for rendering saidwatermark to a second portion of said article; and means for repeatingthe extracting, encrypting, generating and rendering steps with anotherportion of said article until all relevant information of said articlehas been processed and a cryptographic link is formed thereby.
 18. Thecomputer program product according to claim 17, wherein said watermarkis generated based on a selected watermark generating mechanismdependent upon said encrypted information.
 19. The computer programproduct according to claim 18, wherein each of said watermarks isgenerated based on different watermark generation mechanism.
 20. Thecomputer program product according to claim 19, wherein seeds forgenerating a watermark are from only one portion of said article orseveral selected portions of said article.
 21. The computer programproduct according to claim 17, wherein said information is extracteddirectly from text.
 22. The computer program product according to claim17, wherein said information is extracted from one or more invariantfeatures of an image.
 23. The computer program product according toclaim 22, wherein said image depicts biometric data of a personassociated with the article.
 24. The computer program product accordingto claim 17, wherein said article is an electronic document.
 25. Anarticle requiring protection against forgery or fraud, said articleincluding: two or more portions for containing information, saidinformation including text, biometric data, or both; and two or morewatermarks, each watermark printed in a respective one of said portionsand being dependent upon information in a different portion, whereby acryptographic link is formed between said two or more portions.
 26. Thearticle according to claim 25, wherein said article is an electronicdocument.
 27. An article requiring protection against forgery or fraud,said article formed by the steps of: extracting information from a firstportion of said article, said article having two or more portions forcontaining information, said information including text, biometric data,or both; encrypting said extracted information from said first portion;generating a watermark using said encrypted information; rendering saidwatermark to a second portion of said article; and repeating theextracting, encrypting, generating and rendering steps with anotherportion of said article until all relevant information of said articlehas been processed so that two or more watermarks are formed, eachwatermark being rendered in a respective one of said portions and beingdependent upon information extracted from a different portion, whereby acryptographic link is formed between said two or more portions.
 28. Amethod of forming an article requiring protection against forgery, saidmethod including the steps of: generating an invisible watermarkdependent upon information contained in said article; and rendering saidwatermark within an official seal placed on said article, said officialseal being a securely controlled item of an authority.
 29. The methodaccording to claim 28, wherein said article is an electronic document.30. The method according to claim 28, further including the steps of:extracting information from a portion of said article; and encryptingsaid extracted information.
 31. The method according to claim 30,wherein said information is extracted directly from text.
 32. The methodaccording to claim 30, wherein said information is extracted from one ormore invariant features of an image.
 33. The method according to claim32, wherein said image depicts biometric data of a person associatedwith the article.
 34. An apparatus for forming an article requiringprotection against forgery, said apparatus including: means forgenerating an invisible watermark dependent upon information containedin said article; and means for rendering said watermark within anofficial seal placed on said article, said official seal being asecurely controlled item of an authority.
 35. The apparatus according toclaim 34, wherein said article is an electronic document.
 36. Theapparatus according to claim 34, further including: means for extractinginformation from a portion of said article; and means for encryptingsaid extracted information.
 37. The apparatus according to claim 36,wherein said information is extracted directly from text.
 38. Theapparatus according to claim 36, wherein said information is extractedfrom one or more invariant features of an image.
 39. The apparatusaccording to claim 38, wherein said image depicts biometric data of aperson associated with the article.
 40. A computer program producthaving a computer readable medium having a computer program recordedtherein for forming an article requiring protection against forgery,said computer program product including: means for generating aninvisible watermark dependent upon information contained in saidarticle; and means for rendering said watermark within an official sealplaced on said article, said official seal being a securely controlleditem of an authority.
 41. The computer program product according toclaim 40, wherein said article is an electronic document.
 42. Thecomputer program product according to claim 40, further including: meansfor extracting information from a portion of said article; and means forencrypting said extracted information.
 43. The computer program productaccording to claim 42, wherein said information is extracted directlyfrom text.
 44. The computer program product according to claim 42,wherein said information is extracted from one or more invariantfeatures of an image.
 45. The computer program product according toclaim 44, wherein said image depicts biometric data of a personassociated with the article.
 46. An article requiring protection againstforgery or fraud, said article including: a portion containinginformation, said information including text, biometric data, or both;an official seal placed on said article, said official seal being asecurely controlled item of an authority; and an invisible watermarkdependent upon said information and being rendered within said officialseal.
 47. The article according to claim 46, wherein said article is anelectronic document.
 48. An article requiring protection against forgeryor fraud, said article formed by the steps of: generating an invisiblewatermark dependent upon information contained in said article, saidinformation including text, biometric data, or both; and rendering saidwatermark within an official seal placed on said article, said officialseal being a securely controlled item of an authority.
 49. A method ofverifying the legitimacy of an article against forgery, said methodincluding the steps of: inputting said article as two or more portions;extracting at least one watermark from each portion; determining awatermark from information in each portion; comparing said extractedwatermark from one portion with said determined watermark from adifferent portion to determine if a corresponding cryptographic link isfound; and repeating said comparing step until all portions of saidarticle have been processed, said article being verified as a legitimatearticle if all cryptographic links are found between said two or moreportions.
 50. The method according to claim 49, further including thesteps of: scanning said product; and dividing said scanned product intotwo or more portions.
 51. The method according to claim 50, furtherincluding the step of: scanning information from a portion of saidproduct to reconstruct a seed to a generated watermark using acryptographic technique carried out in a process of embedding awatermark in said portion.
 52. The method according to claim 51, furtherincluding the step of: extracting an invariant feature from said scannedinformation to reconstruct said seed.
 53. The method according to claim52, wherein said extracted, invariant feature includes biometric data.54. The method according to claim 51, further including the step of:decrypting said scanned information to reconstruct said seed.
 55. Themethod according to claim 49, wherein a cryptographic link is aself-circle.
 56. An apparatus for verifying the legitimacy of an articleagainst forgery, said apparatus including: means for inputting saidarticle as two or more portions; means for extracting at least onewatermark from each portion; means for determining a watermark frominformation in each portion; means for comparing said extractedwatermark from one portion with said determined watermark from adifferent portion to determine if a corresponding cryptographic link isfound; and means for repeating said comparing step until all portions ofsaid article have been processed, said article being verified as alegitimate article if all cryptographic links are found between said twoor more portions.
 57. The apparatus according to claim 56, furtherincluding: means for scanning said product; and means for dividing saidscanned product into two or more portions.
 58. The apparatus accordingto claim 57, further including: means for scanning information from aportion of said product to reconstruct a seed to a generated watermarkusing a cryptographic technique carried out in a process of embedding awatermark in said portion.
 59. The apparatus according to claim 58,further including: means for extracting an invariant feature from saidscanned information to reconstruct said seed.
 60. The apparatusaccording to claim 59, wherein said extracted, invariant featureincludes biometric data.
 61. The apparatus according to claim 58,further including: means for decrypting said scanned information toreconstruct said seed.
 62. The apparatus according to claim 56, whereina cryptographic link is a self-circle.
 63. A computer program producthaving a computer readable medium having a computer program recordedtherein for verifying the legitimacy of an article against forgery, saidcomputer program product including: means for inputting said article astwo or more portions; means for extracting at least one watermark fromeach portion; means for determining a watermark from information in eachportion; means for comparing said extracted watermark from one portionwith said determined watermark from a different portion to determine ifa corresponding cryptographic link is found; and means for repeatingsaid comparing step until all portions of said article have beenprocessed, said article being verified as a legitimate article if allcryptographic links are found between said two or more portions.
 64. Thecomputer program product according to claim 63, further including: meansfor scanning said product; and means for dividing said scanned productinto two or more portions.
 65. The computer program product according toclaim 64, further including: means for scanning information from aportion of said product to reconstruct a seed to a generated watermarkusing a cryptographic technique carried out in a process of embedding awatermark in said portion.
 66. The computer program product according toclaim 65, further including: means for extracting an invariant featurefrom said scanned information to reconstruct said seed.
 67. The computerprogram product according to claim 66, wherein said extracted, invariantfeature includes biometric data.
 68. The computer program productaccording to claim 65, further including: means for decrypting saidscanned information to reconstruct said seed.
 69. The computer programproduct according to claim 63, wherein a cryptographic link is aself-circle.
 70. A method of verifying the legitimacy of an articleagainst forgery, said method including the steps of: extracting at leastone invisible watermark from an official seal, said official seal beinga securely controlled item of an authority; and comparing said extractedwatermark with verification information to determine if said extractedwatermark matches said verification information indicating that saidarticle is legitimate.
 71. The method according to claim 70, whereinsaid verification information is information identifying said authority.72. The method according to claim 70, further including the step of:generating a watermark dependent upon information forming part of saidarticle to provide said verification information.
 73. The methodaccording to claim 72, wherein said information forming part of saidarticle is biometrics data.
 74. The method according to claim 71,further including the step of: decrypting said watermark.
 75. Anapparatus for verifying the legitimacy of an article against forgery,said apparatus including: means for-extracting at least one invisiblewatermark from an official seal, said official seal being a securelycontrolled item of an authority; and means for comparing said extractedwatermark with verification information to determine if said extractedwatermark matches said verification information indicating that-saidarticle is legitimate.
 76. The apparatus according to claim 75, whereinsaid verification information is information identifying said authority.77. The apparatus according to claim 75, further including: means forgenerating a watermark dependent upon information forming part of saidarticle to provide said verification information.
 78. The apparatusaccording to claim 77, wherein said information forming part of saidarticle is biometrics data.
 79. The apparatus according to claim 76,further including: means for decrypting said watermark.
 80. A computerprogram product having a computer readable medium having a computerprogram recorded therein for verifying the legitimacy of an articleagainst forgery, said computer program product including: means forextracting at least one invisible watermark from an official seal, saidofficial seal being a securely controlled item of an authority; andmeans for comparing said extracted watermark with verificationinformation to determine if said extracted watermark matches saidverification information indicating that said article is legitimate. 81.The computer program product according to claim 80, wherein saidverification information is information identifying said authority. 82.The computer program product according to claim 80, further including:means for generating a watermark dependent upon information forming partof said article to provide said verification information.
 83. Thecomputer program product according to claim 82, wherein said informationforming part of said article is biometrics data.
 84. The computerprogram product according to claim 81, further including: means fordecrypting said watermark.